Note: For systematic learning, you can check the index page of the Instruments in Forensic Science. Here, we listed all the MCQs based on the NTA UGC syllabus.
1. Chromatography was first invented by:
- Ramsey
- Henry
- Pascal
- Leduce
Answer and Explanation
Answer: (1) Ramsey
Explanation:
-> Chromatography was first employed by Ramsey (1905) to separate a mixture of gases and vapors.
-> The experiment was based on selective adsorption on or desorption from solid absorbents such as active charcoals.
-> Following years, Tswett (1906) obtained discrete colored bands of plant pigments on a chromatographic column. He coined the term “chromatography” which means “color writing”
-> Reference: Forensic Science Handbook, Volume I By Adam B. Hall, Richard Saferstein. Pg 466.
2. Modern Gas-chromatography was developed by:
- G.D. Kohler and K. Thide
- Henry and Pascal
- Piobert and Pascal
- Martin and James
Answer and Explanation
Answer: (4) Martin and James
Explanation: Modern Gas chromatography (GC) was invented by Archer J.P. Martin and Anthony T. James in 1952.
Reference: History of gas chromatography- ResearchGate
3. Assertion (A): The volatile compounds can be analyzed by GLC.
Reason (R): Because volatile compounds get precipitated with inert gas in the column.
- Both (A) and (R) are true
- Both (A) and (R) are true but (R) is not the correct explanation of (A)
- (A) is true (R) is false
- (A) is false but (R) is true
Answer and Explanation
Answer: (3) (A) is true (R) is false
Explanation:
-> Correct Reason (R): In GLC, an inert gas serves as the mobile phase that helps carry the sample through the column, but precipitation is not involved.
-> The separation occurs based on the interaction between the volatile compounds and the stationary phase in the column.
-> For volatile compounds, GLC is the best and most suitable choice because of its speed, high-resolution capability, and ease of use.
-> Moreover, at sampling ingestion, the temperature is about 50°C which is favorable for analysis, so that a volatile sample gets easily evaporated which makes it easy to use.
References: Sample Preparation Techniques for Gas Chromatography | Gas Chromatography
4. The following gas is used as carrier gas in GLC:
- Hydrogen
- Argon
- Nitrogen
- Helium
Answer and Explanation
Answer: (4) Helium
Explanation: Helium gas acts as a carrier for the GLC operations. It provides good efficiency and analysis but with a high costing price. Other GLC gas is nitrogen (best efficiency but extremely slow) hence their application is very less.
Reference: Carrier Gas Selection for Capillary Gas Chromatography
5. In chromatography very high number of theoretical plates can be achieved by using
- Normal column
- Capillary column
- Thin layer
- ODS normal bore column
Answer and Explanation
Answer: (2) Capillary column
Explanation: Theoretical plates are hypothetical zones or stages in which two phases establish an equilibrium with each other for separation, and used to indicates column efficiency.
6. In the case of examination of paints, Pyrolysis Gas Chromatography is useful for characterization of:
- Pigment
- Binder
- Lacquer
- None of these
Answer and Explanation
Answer: (2) Binders
Explanation: Binder components of paint are analyzed using Pyrolysis Gas Chromatography.
References: Pyrolysis Gas Chromatography (Sciencedirect)
7. The presence of kerosene in gasoline can be determined by:
(i) HPLC (ii) TLC (iii) GLC (iv) GCMS
- (i) and (ii)
- (ii) and (iii)
- (iii) and (iv)
- (i) and (iv)
Answer and Explanation
Answer: (2) Both TLC and GLC
Explanation: The presence of kerosene can be determined by TLC and GLC. In TLC, kerosene shows a long retardation factor (Rf) of 0.91.
Reference: Identifying Type of Refined Petroleum Products in Environmental Media: Thin-Layer Chromatography (TLC) as a Quick Methodology
8. ECD detector in GLC is most suitable for the detection of:
- Gasolene
- Insecticide
- Metallic poison
- None of the above
Answer and Explanation
Answer: (3) Metallic poison
Explanation: GLC with ECD (Electron Capture Detectors) uses radioactive tritium (or 63Ni) to ionize the carrier gas to detect metallic poison, organochlorine pesticides, and various other halogenated hydrocarbons.
9. Silica gel is used in :
- Paper chromatography
- Thin-layer chromatography
- Low voltage electrophoresis
- High voltage electrophoresis
Answer and Explanation
Answer: (2) Thin-layer chromatography
Explanation: TLC uses a thin-uniform layer of silica gel which is coated on a piece of glass, metal, or plastic. Moreover, silica gel (or the alumina) also acts as the stationary phase.
10. Assertion (A): Derivatization prior to gas chromatography is often desirable.
Reason (R): It changes the separation properties of compounds by the purposeful adjustment of their volatility.
- Both (A) and (R) are incorrect
- (A) is correct, but (R) is incorrect
- Both (A) and (R) are correct
- (A) is incorrect, but (R) is correct
Answer and Explanation
Answer: (3) Both (A) and (R) are correct
Explanation: Derivatization prior to gas chromatography is often desirable because of the following reason:
-> Improve the thermal stability of compounds that have polar functional groups.
-> Change the separation properties of the compound by the purposeful adjustment to their volatility.
-> For the introduction of the detector-oriented tag into a molecule.
11. Effusion separator which is used in GC-MS is basically
- enrichment device
- detector
- ion source
- column
Answer and Explanation
Answer: (1) Enrichment device
Explanation: Effusion separator and various jet membranes were used to minimize the large volume of carrier gas eluting from the GC.
12. In thin layer chromatography the mobile phase is?
- Gas
- Solid
- Liquid
- Vapour
Answer and Explanation
Answer: (3) Liquid
Explanation: In Thin Layer Chromatography (TLC), the mobile phase is liquid solvents or a mixture of liquid solvents. While the stationary phase is silica gel (or the alumina).
13. ECD detector in GLC is most suitable for the detection of:
- Gasolene
- Insecticide
- Metallic poison
- None of the above
Answer and Explanation
Answer: (3) Metallic poison
Explanation: GLC with ECD (Electron Capture Detectors) uses radioactive tritium (or 63Ni) to ionize the carrier gas to detect metallic poison, organochlorine pesticides, and various other halogenated hydrocarbons.
14. Silica gel is used in :
- Paper chromatography
- Thin-layer chromatography
- Low voltage electrophoresis
- High voltage electrophoresis
Answer and Explanation
Answer: (2) Thin-layer chromatography
Explanation: TLC uses a thin-uniform layer of silica gel which is coated on a piece of glass, metal, or plastic. Moreover, silica gel (or the alumina) also acts as the stationary phase.
15. Which of the following laws governs gas-liquid chromatography?
- Henry’s Law
- Piobert’s Law
- Lebuc’s Law
- Beer’s Law
Answer and Explanation
Answer: (1) Henry’s Law
Explanation: According to Henry’s law, the partition of an analyte over the gas phase and liquid phase is the ratio of mole fractions in the vapor phase and the liquid phase.
16. Which of the following is the nature of ODS, Octyl, Phenyl sorbents?
- Polar
- Non-polar
- Ionic
- Surfactant
Answer and Explanation
Answer: (2) Nonpolar
Explanation:
Octadecyl (ODS), Octyl, and Phenyl sorbent in solid-phase extractions are used majorly in reversed-phase extraction of non-polar compounds.
Read More: List of Solid Phase Extraction Sorbents.
17. Thin layer Chromatography is used to identify the following:
- Ink
- Glass
- Saliva
- Paint
Answer and Explanation
Answer: (1) Ink
Explanation: TLC separates individual components of any ink by capillary action making a color graph with a solvent solution of ethanol. Most commonly TLC helpful in ball pen ink analysis.
18. The test to determine conclusively the fuel used is:
- GLC
- HPLC
- TLC
- Flash Point
Answer and Explanation
Answer: (1) GLC
Explanation: Fuel can be conclusively identified by GLC because it first separates and analyzes compounds that can be vaporized without decomposition and all the fuels have such properties.
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